Process to 3-phenoxybenzyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate

ABSTRACT

3-Phenoxybenzyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate is prepared in greater than 90% yield by alcoholysis of lower alkyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates with 3-phenoxybenzyl alcohol. A lower alkyl alcohol, e.g., methanol or ethanol, is generated as a by-product. 
     The process is conducted under reflux at a temperature of at least 100° C. in an inert solvent between approximately stoichiometric amounts of the reactants. The solvent is selected to form an azeotropic mixture with, or boil at a higher temperature than, the lower alkyl alcohol by-product, and the by-product is removed from the mixture by distillation as it is produced. If lower alkyl is methyl or ethyl, n-octane, benzene, toluene, xylene, or mesitylene may be employed, for example. 
     The process is promoted by lower alkyl titanium alkoxide catalysts. The purity of the product 3-phenoxybenzyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, which is obtained as a bottoms residue after stripping the solvent, is high enough, greater than 90%, to be suitable for use in commerce as the pyrethroid insecticide &#34;permethrin&#34; without further purification. The purity is enhanced by the use of only 0.001-0.01 mole of the catalyst per mole of lower alkyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate. To avoid hydrolysis of the catalyst, the reaction is carried out under substantially anhydrous conditions.



